When a patient loses a significant amount of blood from a wound or operation site, that blood must be replaced. Due to the risk of blood-transmitted diseases, however, it is desirable to limit the amount of donated blood that is infused. The supply of replacement blood could also be limited. It is therefore advantageous to collect the blood lost by the patient, processing the blood with a recovery system to remove any bone chips, blood clots or lipids within the collected blood, and then reinfusing it back into the patient. Salvaging a patient's own blood limits the amount of donated blood the patient must receive, thereby reducing the risk of exposure to disease, and reduces the need for replacement blood.
Blood-recovery systems typically suction blood from the wound or operation site through a suction hose leading to a collection reservoir, which is also connected to a vacuum source. The vacuum draws blood into the reservoir via the suction hose. Ordinarily, the path from the hose to the reservoir passes through one or more blood filters. Once the collection reservoir is full, the blood is drained into a collection bag for reinfusion or later use. Generally, in order to drain the blood from the reservoir, it is necessary to break the vacuum within the reservoir by, for example, venting the reservoir to the atmosphere. In many blood-recovery systems, this operation necessarily interrupts the flow of blood since a vacuum is necessary to draw blood into the reservoir.
Various attempts have been made to provide apparatus capable of collecting blood from a patient continuously. For example, U.S. Pat. No. 5,634,893 and U.S. Pat. No. 4,033,345 discloses apparatuses for continuously collecting blood from a patient while simultaneously draining the processed blood from the reservoir. The apparatus is U.S. Pat. No. 5,634,893 includes a first chamber for collecting blood and a lipid separator, which separates undesirable lipids or other buoyant substances from the collected blood, arranged in said first chamber. A vacuum port on the first chamber couples the chamber to a vacuum source. The first chamber is connected to a second chamber into which collected blood drains, located below the first chamber so that blood can drain into the second chamber by gravity through a duckbill drain valve. A selector valve selectably couples the second chamber either to the vacuum source or to a vent. The drain valve closes when the second chamber is vented while the first chamber is coupled to the vacuum source, thereby isolating the chambers from one another and permitting the first chamber to remain under vacuum even as the vented second chamber drains into a blood bag.
However, the known apparatuses capable of collecting blood continuously while allowing drainage of the collected blood for reinfusion are subject to several problems. For example, most such known systems are expensive and mostly only capable of use for a limited time, and only on one single occasion. Further, said known systems are often complicated to use, requiring extensive skills from the operator. Specifically, the system disclosed in U.S. Pat. No. 5,634,893 is intended for one time use, and for use during a limited time period. After a certain time of operation the first chamber will become clogged by lipids and other buoyant substances from the collected blood. Further, the one-way valve arranged between the first and second chamber is unreliable, and problems with inadequate closure might be expected.